Whiplash injuries are among the most common injuries that occur during automobile rear end collisions and account for a large portion of automobile insurance claims. During such a collision, the occupant's head is first thrown backwards relative to the neck and torso, impacts the headrest, and is subsequently thrown forwards. Such an event may cause soft tissue injury and places excessive strain on the neck due to hyperextension, leading to whiplash injury. To reduce whiplash injury, the most common mechanism involves moving the headrest forward such that the distance between the head and the headrest is minimized. Such a mechanism is known as a head restraint mechanism and may be either static or active. The reduced distance between the head and the headrest implies that the relative accelerations between the head and neck, or T1 and C1 vertebrae are reduced, thereby reducing the possibility of whiplash injury.
A disadvantage of existing mechanisms is that the activation of the head restraint mechanism usually occurs only after the occupant has been thrown rearward against the back seat. There still exists a need for a head restraint system that activates in advance of or concurrently with the rearward movement of the occupant's torso and does not rely on expensive sensors and circuitry to detect and activate the head restraint system.